Generally, precast load-carrying concrete systems are pre-manufactured, for example from prestressed concrete, by building them on pretensioning beds. The precast load-carrying concrete systems can be used for construction such as floor and roof systems, parking structures, and bridges. The precast load-carrying concrete systems can also be used as diaphragms to transfer lateral loads to a structure. Specifically, a precast load-carrying concrete floor structure can include a flange or slab and at least one vertical supporting member (also known as a stem). The flange or slab can be reinforced with a carbon fiber reinforcing grid (“C-Grid”) within the flange or slab.